Conventionally, as an ink composition applied to an ink jet recording system, an aqueous ink containing water as a main component and an oily ink containing an organic solvent as a main component have been used. A solventless energy ray-curable ink composition which cures an ink by irradiation with an energy ray (e.g. an ultraviolet ray) has been attracting attention in order to suppress blur of a printed material (e.g. Patent Document 1).
As a means to cure the above-described energy ray-curable ink composition, a low pressure mercury lamp, a high pressure mercury lamp, a super-high pressure mercury lamp, a xenon lamp, and a metal halide lamp have been used. However, a polymerizable compound used in the energy ray-curable ink composition generally has low reactivity and, unless an energy ray having a high energy is radiated, it undergoes oxygen inhibition and sufficient curability is not obtained, and therefore there is a problem that adherability is poor. For this reason, for example, an ink composition with improved adherability, and scratch resistance, using monofunctional and polyfunctional monomers, and 50 to 30% by mass of an oligomer as a polymerizable compound has been proposed (e.g. Patent Document 2).    Patent Document 1: JP-A 5-214279    Patent Document 2: JP-A 2001-525479